Do you have any pictures of the two side by side? Have you verified that the rotor won't rub? I'm tempted to rework what I have, but there is risk without a template.Something like this where you slide the mounting points out and weld, then fill the gap.
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Do you have any measurements of the 2 styles of backing plate? I may measure my 6-lug ones to see if the new rotor overhangs. It's OK if it does, not OK if the rotor hits the bracket.Rotor dia is bigger so backing plate is bigger .